You know autumn has arrived when New Yorkers start talking up their annual weekend migration to Vermont and New Hampshire in pursuit of fall foliage. But why travel so far afield? As Alexander Brash, chief of New York City's Urban Park Rangers, tells us, there's plenty of spectacular leaf-peeping to be had right here in the concrete jungle. Brash recommends Manhattan's last remaining natural forest in Inwood Hill Park, between Dyckman and 218th Streets. Begin your ramble at the Inwood Nature Center at 218th Street and Indian Road, where the Park Rangers' office can provide you with maps and park literature. While you're there, take time to explore Inwood's ancient rock formations, which were used as temporary shelters by Native Americans more than 6,000 years ago, and hike up to the overlook for views of New Jersey's Palisades across the Hudson. Then savor the lack of Sunday-night traffic on the subway ride home.